In Luke 7:18-23 we have a change of participants, a change of theme, and
all of this is introduced in verse 18 by a geographical movement, a key
indicator in Luke of a discourse boundary. A second notable discourse
boundary is evident at Luke 7:23/24. In verse 24 we have a geographical
movement followed by a change of participants and a change of theme.

So what caused the the editors of UBS3 to leave the paragraph unbroken
at Luke 7:23/24? Well the first thing one might jump on is John the
Baptist. The Baptist is a participant in 7:18-23 and he becomes the
subject of discussion in 7:24 ff. I would assume that the editors of
UBS3 might have viewed the Baptist's questions sent to Jesus as some
sort of preliminary to Jesus' discussion of the Baptist 7:24 ff. This
may be the reason for the editorial decision in UBS3. However, I don't
think it is the most significant basis of discourse cohesion in Luke
7:18-28.

As I have pointed out above, there are several reasons based on Luke's
observed methods in marking discourse boundaries to put in a break
between Luke 7:23/24. There is geographical movement, change in theme,
change in focus, change in participants, change in vocabulary and other
changes. However, there is one thematic tie that provides cohesion
across this boundary. The thematic tie is IDENTITY. In Luke 7:18-23 the
issue is the IDENTITY of Jesus as hO ERCOMENOS. In Luke 7:24-28 the
issue is the IDENTITY of the Baptist. Under close observation we
discover that the identity of the Baptist and the identity of Jesus are
in one sense a single topic. This thematic tie pulls these two pericopes
together across the discourse boundary at Luke 7:23/24.

What is the point of all this? The point is that there is a discourse
structure in Luke's narrative above the level of the pericope. The
second point is that discourse boundaries above the level of the
pericope may be difficult to discover using "formal" criteria. I
discovered IDENTITY as a key to the cohesion in this passage, not by
doing analysis of formal criteria but by looking at what the text was
saying (semantics). It was the formal criteria that raised the question.
The formal criteria pointed to a break at Luke 7:23/24.